The present invention relates generally to refractory components used in casting molten metal and, more particularly, to thermal insulative coatings for protecting such refractory components and to enhance their performance while prolonging their service lives.
The insulative coating of the present invention is particularly suited for use on a variety of refractory bodies, such as submerged pouring nozzles, ladle to tundish shroud tubes and like consumable components used in the continuous casting of metals, such as molten steel. Heretofore, in order to protect submerged pouring nozzles, shroud tubes and the like from the thermal shock experienced during start-up of a continuous casting run, it has been common practice to prepare the nozzle in some manner in order to minimize the thermal shock caused by a cold nozzle start-up. One common practice has been to preheat the pouring nozzles prior to casting. Another common expedient to protect against the thermal shock of start-up has been the application of a ceramic fiber-impregnated insulative paper product around the outside of the pouring nozzle. The paper product, while somewhat effective in minimizing thermal shock and resultant cracking problems, is expensive due to the cutting, wrapping and wiring required to size and properly fit the paper sheet around the exterior surface of the refractory nozzle. Of course, the paper coating is not applied to the interior cavities of the nozzle.
In addition to the thermal shock problems, prior pouring nozzles employed in continuous casting operations also experience bridging or freezing of metal between the submerged nozzle and the adjacent walls of the water cooled continuous casting mold. The aforementioned preheating or paper wrapping operations tend to minimize such objectionable bridging, however, all problems are not solved. For example, in the case of the wrapped nozzle, there is an internal build-up of frozen metal due to the fact that the interior of the nozzle has no insulative protection.
The present invention solves many of the time-consuming and expensive problems heretofore encountered in the preparation and use of submerged pouring nozzles and like components used in continuous steel casting operations. The present invention provides an insulative coating for such pouring nozzles and the like which eliminates the need to preheat the nozzle. The coating of the present invention prevents undesirable thermal shock in the nozzle body during start-up and also eliminates unwanted bridging or freezing between the nozzle and the mold during casting. The insulative coating of the invention also covers the interior bore of the pouring nozzle to provide insulation therewithin which prevents unwanted build-up of frozen metal within the nozzle bore during casting.